Cis-Trans Isomers Flashcards
Are Trans or Cis alkenes more stable? Why?
Trans alkenes are more stable than cis alkenes because of the net replusion that is present in the methyl groups of cis-alkenes. Since the trans isomers have methyl groups that are further from each other, steric hinderance does not occur
What is steric hinderance?
the repulsion between e- clouds that occur when atoms or groups are too close to each other
Delocalization of cations allows for ________.
rotation
How do you prevent the addition of oxygen into the bunsen burner?
rotate the valve clockwise
What does rotating the valve of a bunsen burner counterclockwise do?
Increases the addition of oxygen and makes the flame hotter
What is the hottest part of a flame?
Tip of the inner core
The base valve below the bunsen burner changes what?
The height of the flame
Vacuum filtration is (slower/faster) than gravity filtration
faster
What is the cis isomer in the experiment?
Maleic acid
(cis-1,2-ethylenedicarboxylic acid)
What is the trans isomer in the experiment?
Fumaric acid
(trans-1,2-ethylenedicarboxylic acid)
Will a pure sample have a more narrow or wide melting point range?
narrow
What is the chemical equation of the combination reaction that forms maleic acid?
C4H2O3(s) + H2O(l) -> C4H4O4
What steps took place in the formation of maleic acid?
A 100mL beaker with DI water is boiled in a heating apparatus for maleic anhydride to be added. When solution is clear, turn off the burner and remove beaker from heat, cool until room temperature, and then put into ice (with occasional swirling). Vacuum filter the cooled solution and keep the precipitate and filtrate for the next steps
What was the reactant used to form maleic acid?
maleic anhydride (C4H2O3)
Why should the solution be swirled in the beaker occasionally while on ice?
to allow the sample to uniformly cool and break up large chunks of crystal that may form
How is fumaric acid formed?
The filtrate from step one is refluxed (adding HCl and two boiling chips inside the round bottom flask), cooled down, and then transferred into an ice bath to crystalise.
How does refluxing work?
Solution is boiled in a round bottom flask (under a bunsen burner) that evaporates solvent into the condensor, where it is cooled (condensed) by a cold streamline of water and drops back down into the flask.
How is the solubility of each isomer tested?
DI water is added into a test tube containing the two different samples
Maleic acid has a ______ melting point but _______ solubility than fumaric acid
1) lower
2) higher
Fumaric acid has a ______ melting point but _______ solubility than maleic acid
1) higher
2) lower
Why does fumaric acid have a higher melting point than maleic acid?
Because although both molecules hydrogen bond, fumaric acid’s arrangement allows for increased Van Der Waals
Why is maleic acid more soluble than fumaric acid?
Because maleic acid’s net dipole increases the molecules polarity. This net dipole is caused by hydrogen bonds at closer proximities.
How should you generally wash glassware?
Rinse with tap water and then DI water (x3). Make sure to swirl as you rinse to cover the entirety of glassware.
In a reflux condensor, cold wwater enters through the ______ and exits through the _______.
1) bottom
2) top
What does a boiling chip do?
Reduces likelihood of bumping
